PSI - Issue 28

Slobodanka Boljanović et al. / Procedia Structural Integrity 28 (2020) 2370 – 2377 Slobodanka Boljanović et al. / Procedia Structural Integrity 00 (2020) 000 – 000

2371

2

Nomenclature a , b

crack length in depth and surface direction C A , C B material constant in fatigue crack growth law for depth and surface direction da/dN crack growth rate in depth direction db/dN crack growth rate in surface direction K A , K B stress intensity factor in dept and surface direction m A , m B material constant in fatigue crack growth law for depth and surface direction N number of loading cycles to failure P applied force R load/stress ratio S applied stress t thickness of the plate w width of the plate

Subscripts f

failure

maximum value related to the applied load/stress

max

0 initial value For the fatigue analysis of a quarter-elliptical corner crack at the pin-loaded hole, Kim et al. (2003) have employed the Forman crack growth law together with the effective stress-intensity factor and the weight function. Further, Song et al. (2002) have suggested the energy concept and Yamashita et al. (2004) have used the Paris crack growth law with the finite element method for evaluating the propagation of semi-elliptical crack. Antoni and Gaisne (2011) have employed analytical concepts whereas Boljanović et al. (2017) have taken into account the crack growth law proposed by Zhan et al. (2014) and J-integral in the fatigue stability assessment of pin-loaded hole with a surface corner flaw. The goal of this research work is to highlight the damage performance strategy for designing the failure strength of plate-type components. In this context, the fatigue phenomenon due to quarter-elliptical corner cracks is examined through the analytical algorithm. Novel set of formulae is employed to evaluate the component life and to analyze the effects of stress ratio. A discussion on the adopted Huang-Moan crack growth concept, which is extended for part-though corner flaw and crack path evaluation, is also addressed. 2. Stress intensities in the vicinity of crack tip Driving mode in the case of a quarter-elliptical corner crack located in the plate (Fig. 1) is quantified through the fracture mechanics-based formula (Newman and Raju, 1984, Carpinteri, 1994), given by

Q K F S a qec    

(1)

where  K and  S are the stress intensity factor and applied stress range, respectively, and a is the crack growth length in depth direction. Further, crack shape coupled with front face effect is examined through the corrective factor F qec (using M 1 , M 2 , M 3 , g 1 , g 2 ) and the ellipse shape factor Q , expressed as follows:

   

   

2

4

 

  

qec t F M M a 2 1     

t M a 3

g g f f 1 2 

    

(2)

w